Generally speaking, a damaged windshield would be covered if it is cracked or damaged in some way. If it is just old and needs to be replaced then it probably is not covered.
Just because it is covered, though, does not mean that yo will actually get any money nor does it mean that you should even file a claim. It depends on the cost of the replacement as opposed to your deductible. Unless your deductible is extremely small, you will not get a significant amount of money back, and your insurance may go up for filing the claim. Ask your agent if it is worth it, but it is doubtful.
Most small knick-knack everyday damage to a car is not worth filing a claim. Cars do get dinged in normal use.